A new class of composite materials has recently appeared in the composite art. This new material is graphite fiber reinforced glass. This new material, as described in commonly assigned copending U.S. Patent Applications Ser. Nos. 54,098, filed July 2, 1979 now abandoned; 92,168, filed Nov. 7,1979 now U.S. Pat. No. 4,263,367; and 135,375, filed Mar. 28, 1980 now U.S. Pat. No. 4,265,968, has many improved properties such as thermal conductivity, flexural strength, impact resistance, and thermal stability. These materials are generally hot pressed as an admixture of graphite fibers of particular fiber orientation in particulate glass. Therefore, there is generally little difficulty in forming this material in any desired shape prior to hot pressing. Furthermore, it is also possible to hot press the intermediately formed composite into the desired design shape. However, for some applications it is necessary to bond various pieces of these preformed, hot pressed composite materials to metal pieces. Attempts at using conventional bonding materials such as epoxy, while meeting with limited success are not compatible with the high temperature use these composite materials are primarily designed for and particularly adapted to, although for some less stenuous applications, conventional adhesives could be quite acceptable.
Particular problems occur in attempts to bond laser mirror substrates made of such composite materials to metal parts or assemblies such as metal heat exchangers. Because of the temperature gradients such metal-composite bonds undergo in operation of such mirrors, it is difficult to get a bond material of sufficient strength and adhesion to withstand this use.
Accordingly, what is needed in this art is a bonding method for fiber reinforced composites and specifically graphite reinforced glass matrix composites which provides a bond which maintains the strength and thermal properties of the composite, especially when bonded to a metal substrate.